Sharif Digital Repository

In a real-time routing problem, a sequence of requests emerge overtime in a metric and should be served by $k$ moving agents (i.e. the servers) in order to minimize a certain cost function. If the cost function is the average of completion time of the requests, the problem is named \textit{online $k$-traveling repairman problem}. An online algorithm with lookahead would be aware about next arising requests in a specific time-window. We present deterministic and randomized algorithms with competitive ratios $5.829-\delta$ and $3.873-\delta$ against and oblivious adversary, where $\delta$ depends on server's lookahead, specification of metric and last request's release time. We the show... 

Brain Computer Interface (BCI) is a communication system between human brain and a computer or a peripheral device which by recording brain signals directly would send messages and commands from the human brain to computer.According to brain activity patterns of EEG, BCIs are divided into different types. The most important of these patterns called ERP (Event Related Potentials) which appears after particular events in the EEG signal. A significant ERP pattern is P300 potential. It occurs when patient recognizes oddball stimuli. SSVEP (Steady-State Visual Evoked Potential) is another type of patterns and is response of the brain to optical stimulations with certain frequencies and a strong... 

Decision making for planning a petrochemical plant is a difficult task, particularly when decisions are required to be made under constraints and different objectives. Final purpose of current research is to develop a reliable model for selecting limited petrochimal products among all potential alternatives under different constraints, considering two desired objective functions; Maximizing economic gain and minimizing safety risk. The powerful tool of multi objective decision making has been used for solving the proposed model. The developed model has been applied to Jam Petrochemical Company as a case study and the acquired results found to be successful.

 

In this thesis, we quantify the extent to which the self-employed systematically under-report their income in Iran households survey by using expenditure based method. The method applied is an improvement of Pissarides and Weber (1989) method which is based on the Engel curve, describing the relationship between incomes and expenditures. In this method, we can estimate the exact amount of average underreporting instead of offering estimation interval.The relationship between incomes and expenditures of wage and salary workers is used to infer the actual income, and thus the reporting gap, of the self-employed based on their reported expenditures. We find that the self-employed underreport... 

The circular flexible cylindrical liquid tanks usually are made of steel or aluminum and in majority of cases are built on grade due to its economic advantages. The most important part of a safe design of a storage tanks is the accurate estimation of the seismically induced lateral forces that should be transferred to its base through the tank shell and its support. Seismic behavior of liquid storage tanks is quite different from regular buildings and industrial structures due to its nonlinear behavior caused by complex distribution of hydrodynamic pressure, buckling of its walls, etc.. Moreover, the effect of rocking motion caused by the under laying soft soil, on its response parameters... 

The detuning of the structures equipped with Tuned Mass Dampers (TMDs) caused by their nonlinear behavior under strong ground motions is a real concern in their practical application. This thesis presents a feasibility study on the effectiveness of TMDs in reducing the seismic response and the resulting structural damage of reinforced concrete structures under intense ground motion. A number of 2-D concrete moment resisting frames with different numbers of stories are considered. TMDs are used as a mean to protect these structural models against ground excitation. The mass of TMDs are varied from 1% to 5% of the first effective modal mass of the structural models. IDARC 2-D program is used... 

The considerable structural damage caused by near field earthquakes has revealed the need for further research on their characteristics and their corresponding effects on structures. The short-duration, high- energy pulses present in these types of earthquakes impose high demands on the structures compared to far field ground motions. Thus, more research is needed to improve the current design methods, especially from a performance based point of view for the structures close to faults. This study is about damage assessment of steel moment resisting frame structures under near-field ground motions from a performance based design point of view. A number of 3 and 9-story, 3-D structural model... 

Researches carried out on the damages imparted to the building structures under severe earthquakes have shown the importance of asymmetry effects of the buildings on the level of these damages. In these cases, the structures enter into the nonlinear state of their behavior and the structural elements, as well as nonstructural ones undergo large deformations. Additional damping systems have been proposed in many studies to avoid enforcing such large forces on the structures. One example of these systems is viscous fluid damper. The effectiveness of this type of dampers in reduction of the forces has been shown in many previous works. In this research we look for a damping eccentricity which... 

In the current design Codes, the estimation of maximum inelastic Single Degree Of Freedom (SDOF) displacements is done through simplified procedures by either applying modification factors on maximum SDOF elastic displacement demands or by considering equivalent SDOF systems with elongated fundamental period and increased damping ratio. Thus, the inherent uncertainty caused by approximating maximum inelastic displacements with maximum elastic displacements is neglected. On the other hand, in time history dynamic analysis of structures, the free field recorded ground motions are applied to the base of structures. Obviously, this procedure would be correct when the structure is built on firm... 

Buried pipes are among the most important urban infra-structures which are developed to distribute water, gas, oil, etc.. Researchers have already demonstrated that extreme failures which lead to total disruption of the pipelines, both mains and the distribution network, due to permanent ground displacement in fault zones. In order to avoid any disturbance in the regular performance of pipelines and prevention of environmental contamination, there is a need to investigate the vulnerability of pipelines and their seismic retrofitting, if necessary. In the presented study, the method of pipeline retrofitting by high strength CFRP composite is investigated. In that regard, using a 3D model of... 

Near-Field earthquakes have gained so much attention through their catastrophic consequences on structures in the vicinity of seismic sources during recent events. Based on recorded data, it is understood that these kinds of phenomena are often accompanied with a large energy pulse at the first times of record whose impulsive characteristic is primarily caused by “forward directivity”. Incapability of response spectra for depicting great demand for energy dissipation disqualifies this method for utilization. Thus it seems inevitable to analyze the models prone to this kind of hazard using time-history based analysis. Being simple enough in time domain, raises hopes for finding a mathematical... 

The main goal of this research is detection, localization, and determining the severity of structural damages. The importance of this objective is to prevent abrupt destruction and severe human and financial losses. Damage detection is divided into local and global detection, and global detection contains static and vibration-based methods. In this research, the vibration-based method is used. Due to the complexity of this method, accurate and powerful tools are required for detecting effective features in damages; Deep Learning (DL), which is part of a broader family of machine learning methods based on artificial neural networks (ANN), could be used. Accordingly, in this project, the... 

Classic controllers are designed to control the structure response at the desired thresholds concerning the minimum applied force by control elements. In some cases, the minimum applied force does not lead to the minimum energy consumption of the controlling system. Especially, the consumption energy of the semi-active control system is not linearly related to their applied force and their energy consumption is a nonlinear function of system dynamic variables. On the other hand, classic control algorithms are not optimized in the time domain of earthquakes and those are sub-optimal algorithms based on the structure's inherent characteristics. Time domain optimized algorithm control is an... 

The main goal of the current building design codes is to protect life safety, and generally, they do not directly address other societal, economic, etc., concerns regarding earthquakes. However, recent earthquakes around the world have shown that the effects of earthquakes' damages and losses can go beyond life-safety concerns. This observation has led many renowned scholars, organizations, and agencies to state the need to change the current design codes. In this regard, this thesis investigates the basis of setting the seismic design requirements and suggests a method in this respect. The study consists of two main parts. Part I (theory and design methodology) discusses some theoretical... 

The seismic behavior of the non-structural components and their effect on the overall performance of the building structures is among the important issue that should be thoroughly investigated from different aspects such as the resiliency, and the replacing cost. On the other hand, in analysis and design of structures, assuming a rigid under-laying soil is not always right and the effect of soil-structure interaction should be taken into account in certain cases. A flexible support could affect the dynamic characteristics of the structures through elongating their natural vibrating periods as well as increasing their damping ratios, thus should not be ignored. If the period of a... 

This study aims to identify the structural damage using deep learning. Damage to structures reduces their lifespan. Therefore, continuous monitoring of structures is necessary to detect any possible damages that occurred due to various causes. Structural health monitoring systems that use wired sensors to measure signals are costly and time-consuming to install. Whereas, wireless sensor-based damage detection systems are relatively cost-effective. However, one of the most important problems in using them is the loss or non-recording of some data, which severely affects the accuracy of a structural damage detection system. On the other hand, health monitoring using machine learning-based... 

This study evaluated post-tensioned system’s behavior in the steel structure. The post-tensioned system includes post-tensioned frame and gravity system (gravity frame and floor diaphragm) and considers the interaction of post-tensioned frame with gravity frame. Post-tensioned frame is the moment frame that has post-tensioned connections instead of ordinary connections. Bolted top and seat angles are used in the connection, along with post-tensioned high strength strands that run parallel to the beam. The strands compress the beam flanges against the column flange to develop a resisting moment and the friction between the beam and column and the two angles resist shear. Studies showed that... 

Recent studies regarding the damage assessment of structures under severe earthquakes have shown that vertical irregularity of structures have considerable effects on the severity of the induced damages. In these cases, structure enters into its nonlinear behavior, and both structural and nonstructural elements sustain large forces and deformations. In general, nonlinear dynamic procedure (NDP) can provide more realistic results than nonlinear static procedures (NSPs). This is due to consideration of higher modes effects and the shifts in inertial load patterns as the structural system experiences nonlinear behavior. Nowadays, due to the complication of nonlinear dynamic analyses in... 

The tuned mass dampers (TMD) are being used more often in structures to control the wind-induced vibrations. However, their performance during an earthquake deteriorates due to a relatively wide frequency bandwidth of seismic input as well as nonlinear structural behavior. Increasing the mass of TMD to enhance its performance whilst reducing its sensitivity to detuning has its own limitation in terms of deploying large masses at usually the roof level of the building structures. In that regard, the researchers have employed the inerter, a mechanical device that is able to produce relatively large moment of inertias with a relatively small mass of flywheel, to improve the performance of the...